1. Field of the Invention
The present invention relates to a support/shock-absorbing apparatus for securement of structures susceptible to damage by relative movement or vibration. More particularly, the present invention is concerned with improvements in pipe snubbers incorporating a non-Newtonian fluid as the hydraulic fluid.
2. The Prior Art
Historically, developments in chemical processing equipment and steam-powered, electrical generating systems and, more recently, systems utilizing nuclear energy as the prime energy source have led to increased emphasis on equipment safety and protection. In particular, it is extremely important that high-pressure, high-temperature conduits and/or critical cooling fluid systems for nuclear power systems be adequately protected. These conduits must be protected from rupture through (a) normal operating conditions such as vibration and dimensional changes caused by temperature fluctuations of the fluid streams, and (b) catastrophic events such as seismic shock and the like. For example, a safely operating nuclear power system demands an uninterrupted flow of coolant to the reactor core. Coolant failure could cause the reactor core to melt resulting in a catastrophic breachment of the fuel containment means with a resultant release of radioactive debris to the environment.
Accordingly, it has become conventional practice to attach shock-absorbing apparatus, commonly referred to as pipe snubbers, to the particular piping system so as to dampen or otherwise dissipate the energy which would tend to destroy the structural integrity of the piping. In light of the critical nature of the operational reliability of these pipe-snubbing apparatus, the responsible regulatory commissions currently impose extremely stringent operational and safety requirements on pipe.
Historically, pipe snubbers have included both mechanical pipe snubbers and hydraulic pipe snubbers. Mechanical pipe snubbers are usually extremely complex.
Hydraulic pipe snubbers overcome many of the problems inherent in mechanical pipe snubbers but are notorious for their tendency to develop leaks of the hydraulic fluid. Leaks develop in hydraulic pipe snubbers because they are frequently used in hostile environments such as under high temperatures or in areas of high radiation dosages. Under these conditions, a conventional elastomeric seal material, such as rubber, hardens and loses its sealing effectiveness. Leakage of a sufficient quantity of hydraulic fluid will render the hydraulic pipe snubber inoperative as a shock-absorbing device. Accordingly, it has become a conventional practice to assume that leakage of any hydraulic fluid from a hydraulic pipe snubber is an indication of complete failure of the hydraulic pipe snubber thereby requiring its replacement. Frequent replacement of pipe snubbers in a nuclear power plant is a very costly, time-consuming procedure.
The general configuration of most conventional hydraulic pipe snubbers also dictates that it be oriented in a near-vertical working orientation to minimize the foregoing leakage problems. Horizontal applications are, therefore, generally precluded for conventional hydraulic pipe snubbers.
Although the hydraulic pipe snubber avoids certain of the limitations inherent in mechanical pipe snubbers, they are not used as support members unless some form of mechanical support mechanism is incorporated. For example, a shear pin, spring or the like imparts the necessary mechanical support characteristics to the hydraulic pipe snubber.
Additionally, conventional hydraulic pipe snubbers have a tendency to operate in a nearly generally linear fashion; that is, the greater the force imposed upon the hydraulic pipe snubber, the greater the degree of movement permitted by the hydraulic pipe snubber until stopped or snubbed by a rate controlled valve or the like. This has the advantage of accommodating gradual changes in relative pipe position caused by gradual thermal changes and the like.
It would, therefore, be an advancement in the art to provide a pipe snubber which, advantageously, reacts in a near-linear fashion in response to gradual movement of a structural member while reacting in a non-linear fashion under forces rapidly imposed upon the structural member. It would be an even further advancement in the art to provide a pipe snubber utilizing a non-Newtonian material as the hydraulic fluid medium. It would be an even still further advancement in the art to provide a pipe snubber which substantially eliminates the problem of leakage from the snubber cylinder while readily accommodating replacement of leaked fluid.